Cichlids by Sanderling

Theo 400 Watt Heater Failure Could Have Been a Major Disaster

// October 29th, 2009 // Equipment Reviews

I purchased a couple Theo 400 Watt submersible heaters by Hydor  about  a year ago and was impressed by several things; the wattage, its reputed unbreakable glass reputation and something Hydor refers to as PTC which I believe stands for ‘power temperature control’. In my recent vertical bio-tower project I included two of them set up a couple of degrees lower than my set point temperature so that they would kick in after major water changes to rapidly restore the system temperature.

Like so many other heater brands this type has proven it can fail so that the heating element remains energized, no matter what the water temperature is and depending on the volume and heat loss characteristics of your system, can cause  runaway temperature, ultimately ending in the death of your fish. My system is sealed in order to prevent heat and humidity loss into the fish room and as a result, even at 400 gallons, can over heat as a result of a defective 400 Watt heater.

I discovered one this morning  in ‘runaway mode’  and measured my water temperature at 40 degrees Celsius-way too hot! As luck would have it, it seems I only lost 2 fish.

Here are a few things you can do to avoid a heater ’cook off ‘ killing your fish;

1. For larger tanks and systems over a 100 gallons, take the total number of heating watts required for your system/tank and divide by three. Round this number up to the nearest wattage size of a good quality heater and use three units instead of one. If one fails so that it won’t heat, your temperature may drop a couple of degrees, which won’t kill your fish but you will be alerted to a possible problem with your heaters.  For smaller setups, divide by two.
2. Check your heaters at least once every six months and more often as they get older. Remember, most heaters will fail in a mode that has them running continuously, waisting energy and potentially killing your fish!
3. Consider installing a high temperature alarm to alert you if there is a problem. Failing that, use the old hand in the water test at least once a day.
4. Always use ground fault circuit interrupter (GFCI) receptacles or circuit breakers to feed your heaters in case they break and expose live conductors to the aquarium water. Remember electricity and water are poor companions!